This invention relates to a displacement sensor composed of a force sensor, an acceleration sensor or the like, which is capable of performing a precision measurement, and a mobile data collecting apparatus suited to be used for, among others, an on-vehicle navigation system utilizing the displacement sensor.
Displacement sensors of this type have heretofore been known. For example, Japanese Patent Publication (Unexamined) No. 8-248059 discloses a three-dimensional acceleration sensor comprising a weight part and detection parts arranged point-symmetrically at positions equidistantly away in a three-dimensional direction from the center of gravity of the weight part, a three-dimensional acceleration applied to the weight part being detected by the detectors.
The above-mentioned publication discloses sensors of the following types. The first one is of the type in which a piezoelectric element is utilized in a detection part and an acceleration applied in various directions by an adjustment torque screw for clamping or sandwiching a weight part with a constant pressure is detected as an analogous variation in voltage by the piezoelectric element (piezoelectric type acceleration sensor). The second one is of the type in which a magnetic sensor is utilized in a detection part and which includes an electromagnet with the magnetic sensor fixed thereto and a control unit module for it. An amount of displacement of the magnetic body is detected as the variations in magnetic field by the magnetic sensor. Then, the amount of displacement is pulse-width modulated so as to be fed back to the electromagnet and the pulse-width modulation is monitored to detect an acceleration (electromagnetic type acceleration sensor). The third one is of the type which includes a weight part having a magnet of magnetic characteristics, serving as an inertial body and in which a detection part includes magnets three-dimensionally opposedly arranged in an inner surface of a case and a magnetic coil module. With the weight part kept floated within the case under the effect of magnetic suspension from six directions caused by the magnets and the magnetic coil module, the variations in magnetic flux caused by positional change of the weight part are converted into an electric signal and detected as an acceleration (magnet type sensor).
However, the above-mentioned techniques have the following shortcomings.
In the case where a sensing part (weight part) of an acceleration sensor contacts a separate substance (detection part) as in the case with the piezoelectric type acceleration sensor, mechanical errors caused by frictional force thereof are liable to occur.
Even in the structure in which the weight part is balanced in a hollow interior as in the case with the electromagnetic type speed sensor, modulation errors and conversion errors during the pulse-width/electric power conversion are liable to occur because the controlling of the electric power supplied to the electromagnetic coil is performed by means of pulsewidth modulation. This makes it difficult to obtain a precision detection.
Moreover, in any one of the above-mentioned types, there is not only a need of analog processing, such as synchronous rectification and smoothing, amplification, integration and the like but also a need of A/D conversion, for detection of an acceleration. Consequently, it is difficult to obtain more than a certain degree of accuracy because of its non-linearity. Moreover, the circuitry becomes large and the cost is increased. In addition, operation tends to be unstable because it is susceptible to the fluctuations in temperature and power supply.
The present invention has been accomplished in view of the abovementioned shortcomings. It is, therefore, a technical problem to be solved by the present invention to provide a displacement sensor which is precise and inexpensive.
Mobile data collecting apparatuses of the above-mentioned type have heretofore been known, as well. A typical example is disclosed in Japanese Patent Publication (Unexamined) No. 8-43113, in which an absolute position is detected utilizing radio waves from a GPS (Global Positioning System). Another example is disclosed in Japanese Patent Publication (Unexamined) No. 8-297033, in which a position on the ground is computed utilizing a combination of various kinds of sensors (an acceleration sensor, an angular acceleration sensor and an inclination sensor).
However, the former has such shortcomings that it becomes unable to be used in a tunnel, under an elevated railroad and in a room because it uses radio waves coming from an artificial satellite. On the other hand, the latter has such shortcomings that big errors occur depending on accuracy of the sensors and the positions where they are attached, the number of component parts of the sensors and the circuits are increased and therefore, the cost is inevitably increased.
In view of the above situation, it is, therefore, another technical problem to be solved by the present invention to provide a mobile data collecting apparatus which can be used even in a place where radio waves coming from an artificial satellite do not reach, in which errors are lessened and which is inexpensive.
As mentioned above, the present invention has been accomplished in view of the shortcomings inherent in the prior art. It is, therefore, an object of the present invention to provide a displacement sensor which is precise and inexpensive and a mobile data collecting apparatus which can be used even in a place where radio waves coming from an artificial satellite do not reach, in which errors are lessened and which is inexpensive.
In a first embodiment of the present invention, a displacement sensor includes a moving member (10) composed of a magnetic material; a pair of stators (11, 12) each composed of a magnetic material and arranged opposed to each other with respect to the moving member (10), the stators (11,12) including driving coils (13, 14) and position detectors (15,16) corresponding to the driving coils (13, 14), respectively; and a control unit (30) for driving, based on a detection output coming from the position detectors (15, 16), the driving coils (13,14) with an electric power corresponding to intervals (d1, d2) between the moving member (10) and the stators (11, 12) so that the moving member (10) is balanced at an intermediate position between the stators (11, 12) and for computing a force (F) or acceleration (G) applied to the moving member (10) with a driving electric power of the driving coils (13, 14).
In a second embodiment of the present invention, one pair or more of the stators (11, 12) are disposed opposed to each other on each plane of the moving member (10) in triaxial directions X, Y, Z.
In a third embodiment of the present invention, a displacement sensor includes a spherical moving member (10) composed of a magnetic material; three pairs of stators (11, 12) each composed of a magnetic material and arranged opposed to each other in triaxial directions X, Y, Z, with respect to the moving member (10), the stators (11, 12) including driving coils (13, 14) and position detectors (15,16) corresponding to the driving coils (13, 14), respectively; and a control unit (30) for driving, based on a detection output coming from the position detectors (15, 16), the driving coils (13,14) with an electric power corresponding to intervals (d1, d2) between the moving member (10) and-the stators (11, 12) so that the moving member (10) is balanced at an intermediate position between the stators (11,12) and for computing a force (F) or acceleration (G) applied to the moving member (10) with a driving electric power of the driving coils (13, 14).
In a fourth embodiment of the present invention, a shield .(23) composed of a non-magnetic body is interposed between and adjacent to the stators on the X-, Y- and Z-axis.
In a fifth embodiment of the present invention, the driving of the driving coils (13,14) is a pulse driving having a constant pulse-width and a driving electric power is computed based on the number of the pulse driving signal.
In a sixth embodiment of the present invention, the control unit (30) includes a phase comparator circuit (31) for supplying a comparing signal. (Clock) to the paired position detectors (15, 16) and detecting an unbalance of the intervals (d1, d2) between the paired stators (11,12) and the moving member (10) as a difference in phase of the comparing signal (Clock); a pulse generating circuit (32) for supplying a driving pulse (P0, P1) of a constant pulse-width to one of the driving coils (13,14) in accordance with the detected phase difference; a driver circuit (33) for driving the driving coils (13,14) with the driving pulse (P0, P1); a counter circuit (34) for counting the number of the driving pulses (P0, P1); and computing or processing means (40) for computing a force (F) or acceleration .(G) applied to the moving member (10) based on a counted value of the counter circuit (34).
In a seventh embodiment of the present invention, the computing means (40) computes a force (F) applied to the moving member (10) per axis by using an equation of F =K1xc2x7N1xe2x88x92K2xc2x7N2, where N1, N2 represent count numbers of the driving pulses (P0, P1) supplied to the paired driving coils (13, 14) on one axis and K1, K2 represent force coefficients.
In an eighth embodiment of the present invention, the computing means (40) computes an acceleration (G) applied to the moving member (10) per axis using an equation of G=K10xc2x7N1xe2x88x92K2xc2x7N2, where N1, N2 represent count numbers of the driving pulses (P0, P1) supplied to the paired driving coils (13, 14) on one axis and K10, K20 represent acceleration coefficients thereof.
In a ninth embodiment of the present invention, the control unit (30) includes a temperature sensor and makes a correction of the computation of the computing means (40) based on a detection output thereof.
In a tenth embodiment of the present invention, the position detectors (15,16) are converters utilizing the variations in inductance or in electrostatic capacity.
In an eleventh embodiment of the present invention, a mobile data collecting apparatus comprises a hexahedral frame (62) composed of a non-magnetic material; a rectangular parallelepiped moving member (10) composed of a magnetic material, the moving member (10) being loosely fitted so that the moving member (10) can vibrate in a three-dimensional direction within the frame; two pairs of stators (4, 5, 6, 7, 8, 9) each composed of a magnetic body, the two pairs of stators (4, 5, 6, 7, 8, 9) being arranged opposed to each other with the moving member sandwiched therebetween; two pairs of stators (4, 5, 6, 7, 8, 9) each composed of a magnetic body, the two pairs of stators (4, 5, 6, 7, 8, 9) being arranged opposed to each other on three sets of opposed surfaces (62a, 62b, 62c, 62d, 62e, 62f) of the frame with the moving member sandwiched therebetween; the stators being arranged such that three kinds of connecting lines (L1, L2, L3) thereof are orthogonal to each other; a driving coil (13) attached to each of the stators and adapted to vibrate the moving member; a position detecting coil (15) attached to each of the stators and adapted to detect the position of the moving member; moving member control means (63) for driving the driving coils in response to the signal from each of the position detecting coils (15) so that the moving member is located in the center of the frame; acceleration computing means (64) for computing an acceleration of the moving member based on a driving electric power of each of the driving coils; and mobile data computing means (65) for computing a mobile data based on the acceleration computed by the acceleration computing means. By employing this constitution, various mobile data can be obtained from an acceleration of the moving member and without a need for radio waves coming from an artificial satellite.
In a twelfth embodiment of the present invention, a mobile data collecting apparatus comprises a hexahedral frame (62) composed of a non-magnetic body; a rectangular parallelepiped moving member (10) composed of a magnetic body, the moving member (10) being loosely fitted so that the moving member (10) can vibrate in a three-dimensional direction within the frame; two pairs of stators (4, 5, 6, 7, 8, 9) each composed of a magnetic material, the two pairs of stators (4, 5, 6, 7, 8, 9) being arranged opposed to each other on three sets of opposed surfaces (62a, 62b, 62c, 62d, 62e, 62f) of the frame with the moving member sandwiched therebetween; the stators being arranged such that three kinds of connecting lines (L1, L2, L3) thereof are orthogonal to each other; a driving coil (13) attached to each- of the stators and, adapted to vibrate the moving member; a position detecting coil (15) attached to each of the stators and adapted to detect the position of the moving-member; moving member control means (63) for driving the driving coils in response to the signal coming from each of the position detecting coils (15) so that the moving member is located in the center of the frame; acceleration computing means (64) for computing an acceleration and an angular acceleration of the moving member based on a driving electric power of each of the driving coils; and mobile data computing means (65) for computing a mobile data accompanying a rotation based on the acceleration and the angular acceleration computed by the acceleration computing means. By virtue of this constitution, various mobile data accompanying rotation can be obtained from an acceleration and an angular acceleration of the moving member and without a need for radio waves coming from an artificial satellite.
In a thirteenth embodiment, a mobile data collecting apparatus comprises a hexahedral frame (62) composed of a non-magnetic material; a rectangular parallelepiped moving member (10) composed of a magnetic material, the moving member (10) being loosely fitted so that the moving member (10) can vibrate in a three-dimensional direction within the frame; two pairs of stators (64, 65) each composed of a magnetic material, the two pairs of stators (64, 65) being arranged opposed to each other on first opposing surfaces (62a, 62b) of all three sets of opposing surfaces (62a, 62b, 62c, 62d, 62e, 62f) of the frame with the moving member sandwiched therebetween; a pair of stators (66) composed of a magnetic body, the paired stators being arranged opposed to each other on second opposing surfaces (62c, 62d) with the moving member sandwiched therebetween; three pairs of stators (68, 69, 70) each composed of a magnetic body, the three pairs of stators being arranged opposed to each other on third opposing surfaces (62e, 62f) in such a manner as to form a triangular shape thereon with the moving member sandwiched therebetween; a driving coil (13) attached to each of the stators and adapted to vibrate the moving member; a position detecting coil (15) attached to each of the stators and adapted to detect the position of the moving member; moving member control means (63) for driving the driving coils in response to the signal coming from each of the position detecting coils (15) so that the moving member is located in the center of the frame; acceleration computing means (64) for computing an acceleration of the moving member based on a driving electric power of each of the driving coils; and mobile data computing means (65) for computing a mobile data based on the acceleration computed by the acceleration computing means. By virtue of this constitution, various mobile data can be obtained from an acceleration of the moving member and without a need for radio waves coming from an artificial satellite. At the same time, a height (a length in a direction where the stators are opposed on a third opposing surface) of the frame can be reduced.
In a fourteenth embodiment of the present invention, a mobile data collecting apparatus comprises a hexahedral frame (62) composed of a non-magnetic material; a rectangular parallelepiped moving member (10) composed of a magnetic material, the moving member (10) being loosely fitted so that the moving member (10) can vibrate in a three-dimensional direction within the frame; two pairs of stators (64, 65) each composed of a magnetic body, the two pairs of stators (64, 65) being arranged opposed to each other on first opposing surfaces (62a, 62b) of all three sets of opposing surfaces (62a, 62b, 62c, 62d, 62e, 62f) of the frame with the moving member sandwiched therebetween- a pair of stators (66) composed of a magnetic body, the paired stators being arranged opposed to each other on second opposing surfaces (62c, 62d) with the moving member sandwiched therebetween; three pairs of stators (68, 69, 70) each composed of a magnetic body, the three pairs of stators being arranged opposed to each other on third opposing surfaces (62e, 62f) in such a manner as to form a triangular shape thereon with the moving member sandwiched therebetween; a driving coil (13) attached to each of the stators and adapted to vibrate the moving member; a position detecting coil (15) attached to each of the stators and adapted to detect the position-of the moving member; moving member control means (63) for driving the driving coils in response to the signal coming from each of the position detecting coils (15) so that the moving member is located in the center of the frame; acceleration computing means (64) for computing an acceleration and an angular-acceleration of the moving member based on a driving electric power of each of the driving coils; and mobile data computing means (65) for computing a mobile data accompanying a rotation based on the acceleration and the angular acceleration computed by the acceleration computing means. By virtue of this constitution, various mobile data accompanying rotation can be obtained from an acceleration and an angular acceleration of the moving member and without a need for radio waves coming from an artificial satellite. At the same time, a height (a length in a direction where the stators are opposed on a third opposing surface) of the frame can be reduced.
It should be noted that the reference numerals in the parentheses represent corresponding elements in the drawings and that they are employed herein only for the sake of convenience. Accordingly, the present invention is by no means limited to or restrained by the description on the drawings.
FIG. 1 is a front sectional view showing a basic constitution of a uniaxial force sensor which constitutes a displacement sensor according to the present invention;
FIG. 2 is an illustration showing a coil receiving structure of a stator, FIG. 2(a) is a plan view and FIG. 2(b) is a side semi-sectional view;
FIG. 3 is a front sectional view showing a basic constitution of a uniaxial sensor which is different from that of FIG. 1;
FIG. 4 is a front sectional view showing a basic constitution of a uniaxial force sensor which is different from that of FIG. 3;
FIG. 5 is a front sectional view showing a basic constitution of a uniaxial force sensor which is different from that of FIG. 4;
FIG. 6 is a structural diagram showing one embodiment of a displacement sensor of the present invention
FIG. 7 is a structural diagram showing a different embodiment of a displacement sensor from that of FIG. 6;
FIG. 8 is a structural.diagram showing a different embodiment of a displacement sensor from that of FIG. 7;
FIG. 9 is a structural diagram showing a different embodiment of a displacement sensor from that of FIG. 8;
FIG. 10 is a structural diagram showing a different embodiment of a displacement sensor from that of FIG. 9;
FIG. 11 is a structural diagram showing a different embodiment of a displacement sensor from that of FIG. 10;
FIG. 12 is a structural diagram showing a different embodiment of a displacement sensor from that of FIG. 11;
FIG. 13 is a semi-sectional view showing a basic constitution of a triaxial acceleration sensor according to the present invention;
FIG. 14 is a sectional view showing a uniaxial portion of FIG. 13;
FIG. 15 is a circuit diagram of a control unit of a displacement sensor of the present invention;
FIG. 16 is an illustration showing waveforms of various parts of the control unit;
FIG. 17 is a perspective view showing a first embodiment of a mobile data collecting apparatus according to the present invention;
FIG. 18 is a front sectional view of the mobile data collecting apparatus shown in FIG. 17;
FIG. 19 is a control block diagram of a navigation system equipped with the mobile data collecting apparatus shown in FIG. 17; and
FIG. 20 is a perspective view showing a second embodiment of a mobile data collecting apparatus according to the present invention.